A standard workpiece or tool holder for a lathe or like turning machine has as described in the German publication Werkstatt und Betrieb (Carl Hanser Verlag 1991; pages 251-254) a tubular working spindle centered on and rotatable about an axis and an elongated pulling element axially displaceable in the spindle and having a front end provided with at least one holder jaw and a rear end with a forwardly directed face substantially perpendicular to the axis. An actuating body axially displaceable on the pulling element in the spindle forward of the element face has an outwardly directed face and rearwardly inwardly inclined face. A spring braced between the spindle and the body urges the body continuously backward toward the element face. A plurality of wedges in the spindle between the body and the element face each have a rear face flatly abuttable with the element face, an inclined inner face flatly abuttable with the body face, and a forwardly outwardly inclined front face. A support sleeve fixed in the spindle forward of the element face has a face flatly abuttable with the front face of the wedges. Such a holder is particularly usable with steep-angle tools.
When the holder device is in the locked/holding position the pulling element is not only pulled back in the spindle by the springs, which are braced via the actuating body and wedges on the element face, but the wedges also bear forward on the fixed support sleeve and thereby lock the element in the spindle against any significant movement. Thus even if a forward traction that exceeded the spring force were exerted on the element, the element would not move forward into the unlocked/releasing position.
Such a holder is unlocked by back the actuating body against the force of the spring by means of an unlocking pin that is powered normally hydraulically. This allows the wedges to be pushed back into recesses in the actuating body so that they allow this body to move forward, in turn allowing the spindle to move forward. These recesses in the actuating body not only weaken it, but add to the radial dimension of the assembly disadvantageously.